245/60R18 vs 255/65R18 Side-by-side tire size comparison with specs and compatibility
This tire swap is between 3-5% diameter difference. Check for fender clearance and be aware of speedometer error. May require recalibration.
Full Specifications Comparison
| Specification | 245/60R18 | 255/65R18 | Difference |
|---|---|---|---|
| Overall Diameter | 751.2 mm (29.6") | 788.7 mm (31.1") | +37.5 mm |
| Section Width | 245 mm (9.6") | 255 mm (10") | +10 mm |
| Sidewall Height | 147 mm | 165.8 mm | +18.8 mm |
| Circumference | 2360 mm | 2477.8 mm | +117.8 mm |
| Revolutions/Mile | 682 | 650 | -32 |
| Aspect Ratio | 60% | 65% | +5% |
| Rim Diameter | 18" | 18" | 0" |
Key Impact Summary
Speedometer Correction Table
When switching from 245/60R18 to 255/65R18, your speedometer will under-read. Here is the correction at common speeds:
| Speedometer Shows | Actual Speed (mph) | Difference |
|---|---|---|
| 30 mph | 31.5 mph | +1.5 mph |
| 40 mph | 42 mph | +2 mph |
| 50 mph | 52.5 mph | +2.5 mph |
| 60 mph | 63 mph | +3 mph |
| 70 mph | 73.5 mph | +3.5 mph |
| 80 mph | 84 mph | +4 mph |
| 90 mph | 94.5 mph | +4.5 mph |
| 100 mph | 105 mph | +5 mph |
| 110 mph | 115.5 mph | +5.5 mph |
| 120 mph | 126 mph | +6 mph |
What This Swap Means
Wider tires (255/65R18): The 10mm wider contact patch provides better grip in dry conditions and improved cornering stability. However, wider tires increase rolling resistance slightly, which may affect fuel economy by 1-2%. They are also more susceptible to hydroplaning in wet conditions.
Taller sidewall: The 18.8mm increase in sidewall height provides a more comfortable ride by absorbing more road imperfections. Taller sidewalls also offer better protection against pothole damage to wheels. The trade-off is slightly less responsive steering feel.
Ground clearance: Increases by 18.8mm, providing slightly better approach angles for off-road driving and speed bump clearance.